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Description

The CYGNSS level 2 ocean surface heat flux science data record version 3.2 dataset is provided as a service to the oceanographic and meteorological research communities on behalf of the CYGNSS Science Team in direct collaboration with the Cyclone Global Navigation Satellite System (CYGNSS) Mission. CYGNSS was launched on 15 December 2016, it is a NASA Earth System Science Pathfinder Mission that was launched with the purpose of collecting the first frequent space‐based measurements of surface wind speeds in the inner core of tropical cyclones. Originally made up of a constellation of eight micro-satellites, the observatories provide nearly gap-free Earth coverage using an orbital inclination of approximately 35° from the equator, with a mean (i.e., average) revisit time of seven hours and a median revisit time of three hours.
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This dataset provides time-tagged and geolocated ocean surface heat flux parameters with 25x25 kilometer footprint resolution from the Delay Doppler Mapping Instrument (DDMI) aboard the CYGNSS satellite constellation. The reported sample locations are determined by the specular points corresponding to the Delay Doppler Maps (DDMs). Version 3.2 uses CYGNSS Level 2 (L2) Science Data Record (SDR) Version 3.2 surface wind speeds and ECMWF Reanalysis, Version 5 (ERA5). The Coupled Ocean-Atmosphere Response Experiment (COARE) algorithm is what is used in this dataset to estimate the latent and sensible heat fluxes and their respective transfer coefficients. While COARE's initial intentions were for low to moderate wind speeds, the version used for this product, COARE 3.5, has been verified with direct in situ flux measurements for wind speeds up to 25 m/s. As CYGNSS does not provide air/sea temperature, humidity, surface pressure or density, the producer of this dataset obtains these values from this dataset obtains these values from ERA5. This dataset is made available from 1 August 2018 to present with an approximate 1 week latency in the netCDF-4 formatted data files, where each file contains data within a 24-hour UTC period from a combination of up to 8 unique CYGNSS spacecraft. More information on CYGNSS can be found on the CYGNSS mission page.

Product Summary

Platforms
CYGNSS
Instruments
DDMI
Spatial Extent

N: 39.8 S: -39.8 E: 180 W: -180

Spatial Resolution
25000 Meters x 25000 Meters
Geographic Region
GLOBAL ,
TROPICS
Coordinate System
CARTESIAN
Granule Spatial Representation
CARTESIAN
Temporal Extent
2018-08-01
Data Partner
Physical Oceanography Distributed Active Archive Center, Jet Propulsion Laboratory, NASA (NASA/JPL/PODAAC) ,
Cyclone Global Navigation Satellite System Mission, NASA Earth Science System Pathfinder, University of Michigan (NASA/ESSP/UMICH/CYGNSS)
Concept ID
C2927907727-POCLOUD
Data State
ACTIVE
Number of Files/Granules
2685
Processing Level
2
Published
Updated
Science Keywords
Heat Flux ,
Sea Surface Temperature

Citation

Citation is critically important for dataset documentation and discovery. This dataset is openly shared, without restriction, in accordance with the EOSDIS Data Use and Citation Guidance.

Copy Citation

CYGNSS. (2024). CYGNSS Level 2 Ocean Surface Heat Flux Science Data Record Version 3.2 [Data set]. NASA Physical Oceanography Distributed Active Archive Center. https://doi.org/10.5067/CYGNS-L2H32 Date Accessed: 2025-12-13

Documents

USER'S GUIDE

ALGORITHM THEORETICAL BASIS DOCUMENT (ATBD)

ANOMALIES

DATA CITATION GUIDELINES

PUBLICATIONS

GENERAL DOCUMENTATION

Variables

Variables are a set of physical properties whose values determine the characteristics or behavior of something. For example, temperature and pressure are variables of the atmosphere. Parameters and variables can be used interchangeably. Variable level attributes provide individual information for each variable.

The Name in this table is the variable name. Fill value indicates missing or undefined data points in a variable. Valid range is the range of values the variable can store. Scale factor is used to increase or decrease the size of an object and can be used to correct for distortion. For questions on a specific variable, please use the Earthdata Forum.

Name Description Units Data Type Fill Value Valid Range Scale Factor
air_density Air density at surface received from the ERA5 variable &#039;p140209&#039; kg m-3 float -9999 N/A 1
air_temperature 2 meter air temperature received from the ERA5 variable &#039;t2m&#039; K float -9999 N/A 1
antenna The CYGNSS nadir antenna that received the reflected GPS signal associated with the DDMs utilized to derive wind_speed. 0 = none 1 = zenith (never used) 2 = nadir_starboard 3 = nadir_port 1 byte -99 N/A 1
boundry_layer_height Boundry layer height received from the ERA5 variable &#039;blh&#039; m float -9999 N/A 1
cygnss_l2_sample_index A sample index for the corresponding CYGNSS L2 sample index used for deriving the heat fluxes. This can be used with &#039;source&#039; to look up the CYGNSS L2 data and metadata. N/A int N/A N/A 1
dew_point_temperature 2 meter dew point temperature received from the ERA5 variable &#039;d2m&#039; K float -9999 N/A 1
lat The latitude of the heat fluxes. degrees_north float -9999 N/A 1
lhf The latent heat flux estimates at each specular point using the CYGNSS Level-2 wind_speed FDS minimum variance product. W m-2 float -9999 N/A 1
lhf_uncertainty Standard deviation of the additive latent heat flux error, based on known and reported uncertainties from CYGNSS L2 FDS winds, and ERA5 temperature and humidity. Dependent on lhf, in W m-2. W m-2 float -9999 N/A 1
lhf_yslf The latent heat flux estimates at each specular point using the CYGNSS Level-2 YSLF product. W m-2 float -9999 N/A 1
lhf_yslf_uncertainty Standard deviation of the additive latent heat flux error, based on known and reported uncertainties from CYGNSS L2 YSLF winds, and ERA5 temperature and humidity. Dependent on lhf_YSLF, in W m-2. W m-2 float -9999 N/A 1
lon The longitude of the heat fluxes degrees_east float -9999 N/A 1
prn_code The PRN code of the GPS signal associated with the DDMs utilized to derive heat fluxes. Ranges from 0 to 32. 0 = reflectometry channel idle. 1 to 32 represent a PRN code. 1 byte -99 N/A 1
quality_flags Set of status flags, set to 1 if condition is true. Flag bit masks: 1 = poor_overall_quality: The logical OR of the following flags. If any one of the following flags are set then poor_overall_quality will be set: low_range_corrected_gain OR cygnss_l2_fds_fatal_flag OR low_fds_wind_speed OR low_yslf_wind_speed OR high_fds_wind_speed OR high_yslf_wind_speed OR cygnss_l2_yslf_fatal_flag 2 = spare_1, Always zero 4 = low_range_corrected_gain, Range corrected gain is less than 3 8 = ascending_satellite, satellite is on the ascending node of the orbit (subsatellite point latitude is increasing) 16 = cygnss_l2_fds_fatal_flag, CYGNSS Level-2 FDS sample flag is set to fatal 32 = low_fds_wind_speed, CYGNSS Level-2 FDS wind speed &lt; 0 m/s 64 = low_yslf_wind_speed, CYGNSS Level-2 YSLF wind speed &lt; 0 m/s 128 = high_fds_wind_speed, CYGNSS Level-2 FDS wind speed &gt; 25 m/s 256 = high_yslf_wind_speed, CYGNSS Level-2 YSLF wind speed &gt; 25 m/s 512 = cygnss_l2_yslf_fatal_flag, CYGNSS Level-2 YSLF sample flag is set to fatal N/A short -9999 N/A 1
sample The netCDF coordinate variable associated with the sample dimension, which enumerates the zero-justified index range of the DDM time instants contained in the file. 1 int N/A N/A 1
sample_time The mean of ddm_timestamp_utc of the DDMs that were utilized to derive the heat fluxes. Note that the DDM sampling period is not synchronized with the UTC change of second so sample_time can occur at any time relative to the UTC change of second. seconds since 2018-08-02 00:00:00.999 double N/A N/A 1
shf The sensible heat flux estimates at each specular point using the CYGNSS Level-2 wind_speed FDS minimum variance product. W m-2 float -9999 N/A 1
shf_uncertainty Standard deviation of the additive sensible heat flux error, based on known and reported uncertainties from CYGNSS L2 FDS winds, and ERA5 temperature and humidity. Dependent on shf, in W m-2. W m-2 float -9999 N/A 1
shf_yslf The sensible heat flux estimates at each specular point using the CYGNSS Level-2 YSLF product. W m-2 float -9999 N/A 1
shf_yslf_uncertainty Standard deviation of the additive sensible heat flux error, based on known and reported uncertainties from CYGNSS L2 YSLF winds, and ERA5 temperature and humidity. Dependent on shf_yslf, in W m-2. W m-2 float -9999 N/A 1
solar_time Apparent solar time at the subsatellite point seconds since 00:00:00 float -9999 N/A 1
spacecraft_id The CCSDS spacecraft identifier: 0xF7 (247): CYGNSS 1 0xF9 (249): CYGNSS 2 0x2B ( 43): CYGNSS 3 0x2C ( 44): CYGNSS 4 0x2F ( 47): CYGNSS 5 0x36 ( 54): CYGNSS 6 0x37 ( 55): CYGNSS 7 0x49 ( 73): CYGNSS 8 0x00 ( 0): end to end simulator 0x0E ( 14): engineering model 0x0D ( 15): default 0xFF (255): unknown 1 short -9999 N/A 1
spacecraft_num The CYGNSS spacecraft number: Ranges from 1 through 8 and 99. 1 through 8 are on-orbit spacecraft. 99 is the CYGNSS end-to-end simulator. 1 byte -99 N/A 1
surface_pressure Surface pressure received from the ERA5 variable &#039;sp&#039; Pa float -9999 N/A 1
surface_skin_temperature Surface skin temperature received from the ERA5 variable &#039;skt&#039; K float -9999 N/A 1
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